The disclosed technique improves display resolution by reducing the number of transistors in each pixel. The switch transistor is shared between several pixel circuits in several adjacent sub-pixels. A need exists for an improved display resolution and manufacturing yield while at the same time enabling normal sequential scan programming of the display.
Most backplane technologies offer only one type of thin-film transistor (TFT), either p-type or n-type. Thus, the device-type limitation needs to be overcome to enable integration of more useful circuitry onto the display substrate, which can result in better performance and lower cost. The main circuit blocks for driving active-matrix organic light-emitting device (AMOLED) circuits include current sources (or sinks) and voltage-to-current converters.
For example, p-type devices have been used in conventional current mirror and current sources because the source terminal of at least one TFT is fixed (e.g., connected to VDD). The current output passes through the drain of the TFT, and so any change in the output line will affect the drain voltage only. As a result, the output current will remain constant despite a change in the line voltage, which undesirably leads to high output resistance current sources. On the other hand, if a p-type TFT is used for a current sink, the source of the TFT will be connected to the output line. Thus, any change in the output voltage due to a variation in the output load will affect the gate-source voltage directly. Consequently, the output current will not be constant for different loads. To overcome this problem, a circuit design technique is needed to control the effect of source voltage variability on the output current.
A need also exists for improving the spatial and/or temporal uniformity of a display, such as an OLED display.